The following relates to the lighting arts. It especially relates to high intensity light emitting diode chip packages, components, apparatuses, and so forth, and to methods for producing such packages, and will be described with particular reference thereto. However, the following will also find application in conjunction with other solid state light emitting chip packages such as vertical cavity surface emitting laser packages, and in conjunction with methods for producing such other packages.
The use of sub-mounts in packaging light emitting diode chips, semiconductor laser chips, and other light emitting chips is well known. The light emitting chip or chips are attached to the sub-mount by soldering, thermosonic bonding, thermocompressive bonding, or another thermally conductive attachment. The light emitting chips are electrically connected to bonding pads or other electrical terminals disposed on the sub-mount by wire bonding, flip-chip bonding, or another suitable technique. In some approaches, the light emitting chip is attached to the sub-mount and in thermal contact with the sub-mount, but is electrically connected by wire bonds to a circuit such that the sub-mount is not part of the electrical circuit.
In a manufacturing setting, a plurality of light emitting chips are typically attached in parallel rows, or in another layout, to a large-area sub-mount wafer. The attached light emitting chips are transfer molded or otherwise encapsulated on the sub-mount wafer. Optionally, the encapsulant includes a dispersed phosphor for performing a selected wavelength conversion. For example, a group-III nitride based light emitting diode chip emits light in the blue to ultraviolet range, and a suitable phosphor can be incorporated into the encapsulant to convert the blue or ultraviolet emission into white light. The sub-mount wafer is then diced to separate individual light emitting packages, each including one or more of the attached and encapsulated light emitting chips along with a supporting portion of the sub-mount wafer.
Typically, the dicing of the sub-mount wafer is performed by mechanical sawing or scribing. Such mechanical separation processes are readily automated, and are advantageously relatively independent of material characteristics; hence, the mechanical sawing or scribing can simultaneously cut through the transfer-molded encapsulant and the sub-mount. However, mechanical separation processes are problematic in the case of sub-mounts of harder materials, such as aluminum nitride, sapphire, and the like. For these materials, a diamond-coated saw blade or a diamond-tipped scribe is used. Diamond-coated saw blades are relatively thick and generally produce cut widths or kerfs of 150 microns or wider, which adversely impacts device density on the sub-mount wafer. Diamond tipped scribes may produce narrower cut widths or kerfs; however, the scribe depth is limited. Hence, thicker sub-mounts cannot be diced by scribing unless the sub-mount is substantially thinned.
Both sawing and scribing effectively cut through any encapsulant material disposed in the dicing lanes. However, both techniques can produce roughened, striated, or otherwise damaged sidewalls that reduce light extraction efficiency. Moreover, mechanical sawing or scribing produces shear forces that tend to delaminate the encapsulant, which can adversely impact device yield.
The following contemplates improved apparatuses and methods that overcome the above-mentioned limitations and others.